The present invention relates to an apparatus and a method of thermal process for evaporating a solvent for a resist coated on substrates such as semiconductor wafers, LCD substrates (glass substrates used for liquid-crystal displays) and a method of forming a pattern on each substrate including the thermal processing method.
Photo lithographic techniques in process for manufacturing semiconductor devices and LCDs, etc., include the following steps.
Firstly, a resist solution is applied on a substrate such as a semiconductor wafer (called wafer hereinafter) to form a resist film. The resist film is exposed to a desired pattern through a photomask. A patterned resist film is then formed through a developing process.
Chemical-amplifying-type resist is one of resist solutions. This type of resist will generate acid when exposed. The acid acts as a catalyst when dispersed in thermal process to dissolve or change the molecular structure of a base resin as the major component of the resist. Through this procedure, the chemical-amplifying-type becomes soluble.
Photolithographic procedure in a processing system in which a coating and developing apparatus for resist-solution coating and developing processes and an exposing apparatus is connected includes the following steps.
After a wafer has been coated with a resist solution, it is heated to a predetermined temperature for evaporating a solvent for the resist solution. The wafer is then cooled to another predetermined temperature before exposed by the exposing apparatus. The exposed wafer is heated again to still another predetermined temperature for promoting acid-resolving reaction to a developing solution (resist-developing reaction). The wafer is cooled again to further predetermined temperature for protecting it from exceeded resolving reaction, followed by coating of a developing solution for developing process.
The thermal process after resist coating is performed for a wafer set, for a predetermined period, on a heating plate adjusted to a predetermined temperature in a processing chamber, for example.
This thermal process is performed for evaporating a resist solvent as described above. For this purpose, the chamber gas discharged while a purge gas such as air is flowing into the processing chamber so that the evaporated components of the resist solvent will not be accumulated in the processing chamber. The evaporated components are taken out with a flow of the purge gas.
Chemical-amplifying-type resists, however, have a characteristic of causing variation in pattern width after developing process. The inventers for this invention have found a correlation between the uniformity of pattern width and a flow of purge gas in a processing chamber. In detail, it has been founded that the more the flow of purge gas, the worse the uniformity of pattern width.
The uniformity of pattern width will become better when a flow of purge gas is stopped in a processing chamber. Nonetheless, no flow of purge gas causes accumulation of evaporated components of a resist solvent in the chamber and also a flow of evaporated components to the outside when a wafer is taken out from the chamber.
The processing system described above has a resist-coating unit, a developing unit, a heating unit for use after resist coating, a cooling unit, etc, which are aligned along a wafer-transfer passage.
A flow of evaporated components from the heating unit could, for example, soil the inside of the coating and developing apparatus and a clean room.
Once the processing system has been soiled inside and outside, which could cause harmful effects to the procedure such as a resist-coating process, and resulting in low yields.
Not only that, the evaporated components could be attached to the inner wall of the processing chamber or wafer again, which could cause generation of particles, also resulting in low yields.
A purpose of the present invention is to provide a thermal processing apparatus, a coating and developing apparatus having a thermal processing apparatus, a method of thermal and developing processes and a pattern-forming method for enhanced uniformity of coated films after heated, which provides uniformity of coated film after thermal process, and particularly, for enhanced uniformity of pattern width after developed, for example, for thermal process after resist coating by controlling the amount of inert gas flown into a processing chamber or density of a resist solvent.
The present invention provides a thermal processing apparatus including: a processing chamber in which a heating plate is provided, a substrate coated with a coating solution being placed on the heating plate while the plate is heated to a predetermined temperature for heating the substrate; a gas supply passage for supplying an inert gas into the processing chamber; an exhaust passage for discharging the inert gas from the processing chamber to outside; a first flow amount regulator provided along the gas supply passage, for regulating a flow amount of the inert gas supplied into the processing chamber; a second flow amount regulator provided along the gas exhaust passage, for regulating a flow amount of the gas discharged from the processing chamber; and a controller for controlling the first and the second flow amount regulators so that the substrate is heated by the heating plate while the inert gas is circulating in the processing chamber at an extremely small first circulating amount, and then heated while the inert gas is circulating in the processing chamber at a second circulating amount larger than the first circulating amount.
Moreover, the present invention provides a coating and developing apparatus including: a carrier table on which at least one carrier containing a plurality of substrates is placed; a processor for coating a resist on each substrate taken out from the carrier and developing the substrate after exposure; a processing chamber in which a heating plate is provided, the resist-coated substrate being placed on the heating plate while the plate is heated to a predetermined temperature for heating the substrate to evaporate a solvent for the resist; a gas supply passage for supplying an inert gas into the processing chamber; an exhaust passage for discharging the inert gas from the processing chamber to outside; a first flow amount regulator provided along the gas supply passage, for regulating a flow amount of the inert gas supplied into the processing chamber; a second flow amount regulator provided along the gas discharged passage, for regulating a flow amount of the gas discharged from the processing chamber; and a controller for controlling the first and the second flow amount regulators so that the substrate is heated by the heating plate while the inert gas is circulating in the processing chamber at an extremely small first circulating amount, and then heated while the inert gas is circulating in the processing chamber at a second circulating amount larger than the first circulating amount.
Furthermore, the present invention provides a thermal processing method including the steps of: a step of placing a substrate coated with a coating solution on a heating plate in a processing chamber in which an inert gas is circulating; a first thermal-process step of heating the substrate on the heating plate while the inert gas is circulating at an extremely small first circulating amount; and a second thermal-process step of heating the substrate on the heating plate while the inert gas is circulating at a second circulating amount larger than the first circulating amount.
Moreover, the present invention provides a pattern forming method including the steps of: a step of coating a substrate surface with a resist; a step of placing the resist-coated substrate on a heating plate in a processing chamber in which an inert gas is circulating; a first thermal-process step of heating the substrate on the heating plate to evaporate a solvent for the resist while the inert gas is circulating at an extremely small first circulating amount; a second thermal-process step of heating the substrate on the heating plate to evaporate the solvent while the inert gas is circulating at a second flow amount larger than the first circulating amount; a step of exposing the substrate from which the solvent has been evaporated by the heating steps; and a resist-pattern forming step of forming a resist pattern on the exposed substrate by developing.
Furthermore, the present invention provides a thermal processing apparatus including: a processing chamber in which heating means is provided, a substrate coated with a coating solution with a solvent being placed on the heating means while the heating means is heated to a predetermined temperature for heating the substrate; a gas supply passage for supplying an inert gas into the processing chamber; an exhaust passage for discharging the inert gas from the processing chamber to outside; a first flow amount regulator provided along the gas supply passage, for regulating a flow amount of the inert gas supplied into the processing chamber; a second flow amount regulator provided along the gas exhaust passage, for regulating a flow amount of the gas discharging from the processing chamber; a sensor for detecting density of the solvent in the processing chamber; a controller for controlling the first and the second flow amount regulators, based on the density detected after the start of heating, so that an exhaust amount of the inert gas becomes a predetermined amount for a predetermined period until the solvent density reaches a predetermined density, and performing a control process so that the solvent density reaches the predetermined density when it has not reached or exceeded the predetermined density after the predetermined period has elapsed.
Furthermore, the present invention provides a thermal processing method including the steps of: a step of placing a substrate coated with a coating solution with a solvent on heating means in a processing chamber while an inert gas is circulating in the processing chamber; a step of detecting density of the solvent in the processing chamber; a step of controlling supply and exhaust amounts of the inert gas, based on the density detected after the start of heating, so that an exhaust amount of the inert gas becomes a predetermined amount for a predetermined period until the solvent density reaches a predetermined density; and a step of performing a control process so that the solvent density reaches the predetermined density when the solvent density has not reached or exceeded the predetermined density after the predetermined period has elapsed.